Depth Sounder Transducer Mount

[delmitch2]

I have a transom/external mounting depth transducer that I'd like to mount on my M. I REALLY don't want to drill any holes in the hull and am toying with the idea of mounting it on a length of aluminum flatbar, which would in turn be thru-bolted using the extra threads available on my engine mount. Any suggestions or photos of installations would be appreciated.

[dclark]

Not sure about the M. I have mine mounted on the transom of my X. I did something similar to what you are saying. I mounted the transducer to a long bracket (maybe 8" if I had to guess - it's been awhile) at one end and mounted the other end to the boat. I still drilled the holes thru the hull but this way it gets the transducer down far enough to work and keeps the holes above the water line.

I don't much care for the setup, but I don't hate it either. The biggest problem is that although the transducer flips up, a part of the plastic is still in the water (like an algae magnet, since I keep mine in a slip). It works well when motoring even at high speeds. Forget about it when sailing, but then that's probably true with anything and not a time when I really use it anyway.

A lot of people have mounted it in the bilge and let it "shoot thru" the hull. It should work as long as you don't try to "shoot thru" your ballast tank and you mount it in something that stays wet. Plumbers putty is said to work. I think there are some oils you can use as well (but not sure on what kinds).

I'm not sure where it'll end up if you use the existing motor threads. If it's anywhere near your prop, it probably won't work. It needs to be in a less turbulant area.

[Kevin]

I did the plumber's putty on my 26m.

I have a Lowrance fishfinder/depth sounder. It came with a bracket to mount it externally, but I tend to rub things off so I don't want to mount anything more on the hull than needed.

I ran the transducer wires to the steering pedestal and left the transducer loose. Then I went out on the lake and anchored in a reasonably shallow area. Pressed the transducer against the bottom of the bilge until I got a spot where it gave a reasonable reading and put a handfull of plumbers putty down. Pressed the transducer into it and then rocked the transducer until the fish images were nice little triangles. It's sitting in a corner against the ballast tank and a bulkhead so it's well protected from shifting stored items.

The unit seems to work well motor or sail in lakes and rivers. I haven't actually taken a physical sounding to compare, but the readings all appear real close. Even gives an accurate reading of the water temperature.

I did get some odd readings when going to Catalina Island and on the trip to Ensenada. In the open ocean there were times when the reading just went crazy. It would alarm then stop at about 6 feet depth and flash.

This behavior is in the open ocean where the charts say it is crazy deep so I can't understand what it could have been reading. I'd give up and shut the unit off. When I turn it back on as I neared port or an anchorage everything was fine. It's never done this in port or on a lake or river.

Any ideas?

[Duane Dunn, Allegro]

Mine is transom mounted, two screws, no big deal. It's outboard of the port rudder. The glass is really thick at the base of the transom, the screws don't go all the way through. The ballast tank does not extend all the way to the transom, at least on an X, it just has a small channel that goes to the fill valve. I have no problems with it under sail or power. There is one speed, around 9 knots where the water at the transom is full of bubbles and it can be a bit flakey then. As with most of the transducers shipped with the units it is the lowest wattage Lowrance offers and also low frequency. This limits it's ability to penetrate very deep. The bottom goes away between 200' and 300'. It will give all sorts of weird readings when it has lost the bottom. Sometimes it displays the message "Sonar Unit Not Responding", sometimes it doesn't. I do find that occasionally it gets kicked up by some debris, but it's rare. My boat is on a trailer so I don't have problems with bottom growth.

On my previous boat I did a shoot through installation. This worked very good. The key is to have no air spaces between the transducer and the water. While many seem to get by with plumbers putty I wouldn't want to trust an installation like that. It's adhesion is not great and with vibration will certainly come loose eventually, most likely at the worst time. You also have to get any voids out of the putty or the install will not work all the time. Obviously this type of install must be done where there is no ballast tank. There are a number of centerline locations that do not have ballast tank, mainly under the aft berth.

My install was far more reliable although much more permanent. I bedded the transducer in epoxy per the manufactures instructions. I was using a transducer puck specifically made to be installed like this. It comes beveled for the hull shape and everything. You just build a small dam, mix up a batch of epoxy, fill the pool and press the transducer into it. Avoid bubbles when you stir the epoxy. You can test the location by filling the area with water first. This is the only kind of shoot through install I would trust.

The other choice is an oil install. To do this you use a large diameter tube, say 4" pvc pipe, bevel it to the hull contour so the pipe is vertical, then bond it to the hull. Fill it with mineral oil, drop the transducer in and somehow secure it so it stays pointing down, and then cap it once you make a provision for the wire to exit. Seems like a lot of trouble to me.

[Moe]

That's good news about the X, Duane. Thanks!

[dee]

by any chance any of you guys interested in buying a Hummingbird Piranha 1 depth/fish finder? I opened the box but never used it. Its still new.

[Andy26M]

I put a sonar/temp/water speed transducer on my 26M.

To locate it, I epoxied a round disk of plastic (cut out of a cheap plastic cutting board) onto the outside of the hull right where the foot of the stock swim ladder hits. This holds the ladder far enough out so that the transducer fits behind the ladder, and below the middle step. Hence, when swimming and getting in and out of the boat, the ladder actually protects the transducer from being stepped on accidentally.

On the 26M, the ballast tank does extend all the way to the transom (the fill valve is right out on the transom). So, I went ahead and drilled through to mount the transducer - I sealed it very good with silicone, but if it ever leaks, the water will be going into the ballast tank.

This places the tranducer to the right of the motor but inside the starboard rudder. The location meets all the specifications in the tranducer owner's install manual. So far, the only time it goes flaky is when the boat is heeled to port more than 25 degrees or so and the tranducer lifts up in the air. Under power, even with ballast empty at w.o.t., the tranducer is clear enough of the engine that it still works fine.

As to fouling, I have not been able to find bottom paint that is safe for plastic. On a different forum, I got info that "Bag Balm" works well for a few weeks at a time to keep growth off of things. "Bag Balm" is a moisturizer product originally made for use on cows' udders in the winter - i.e. it is pretty heavy duty. You can find it at hardware stores, ACME, and places like that usually. I just bought some, have yet to try it out.

- AndyS

[RBuckingham]

On my M, the transducer is mounted same as above, starboard side inside the rudders. The only thing that does not seem to be reliable is speed over water when sailing due to cavitation turbulance at the stern. GPS readings os speed over land is steady, but water speed bounces around as swells and waves hit the stern.

[Duane Dunn, Allegro]

It would be interesting to see what the actual config of the M ballast tank is. While the fill valve is at the transom just like the X, you may find that the actual body of the tank does not extend to the transom all the way across.

On the X, there is channel that extends from the transom about a foot or so forward to the tank. Under the aft berth there is one shallow tank cavity. The tank then splits into two channels that go forward along each side, then join into the larger main tank cavity at the raised area forward where the step goes up next to the galley.

You can see it most clearly in the brochure photo that shows the parts of the boat all lined up before assembly.

From the line drawings it looks like the M tank is also a multi compartment structure with connecting channels. This is how they get the main cabin foot wells for the standing headroom.

[mgg4]

I did the plumber's putty on my 26m.

I did get some odd readings when going to Catalina Island and on the trip to Ensenada. In the open ocean there were times when the reading just went crazy. It would alarm then stop at about 6 feet depth and flash.

This behavior is in the open ocean where the charts say it is crazy deep so I can't understand what it could have been reading.

I had the same problem at Lake Oroville near Chico, California. The lake is very deep in spots, and my Garmin 188i freaked out. It seems that if the depth is over 500' deep, the Garmin just stops working. Mine was flashing 2-feet of depth, but I knew I was in about 540' of water.

I have a tri-mode (depth/speed/temp) transducer, mounted on the port transom, just inside the port rudder position. Seems to work fairly well. It's far enough outside the prop circle that I don't have any problems with cavitation damage, and close enough to centerline that it doesn't pull up out of the water when sailing, except on an extreme heel on port tack.

--Mark

[delmitch2]

Thanks for all the input. I have a plan now in mind, distilled from all the suggestions. I have purchased some 1/4" aluminum flat bar, 3" x 10". I plan to tap a couple of of holes and attach the xducer to the bottom of the bar. I have 4 x 3/8" carriage bolts that the flat bar will be attached to the transom with. The attachment point will be above the waterline, port side (above the drainage hole from the motor well). I am actually going to place the bar over the hole and drill it out. I can then run the xducer cable through the drainage hole and neatly have it join the throttle cables as they enter the boat on the starboard side of the motor well.
The transducer will be inboard of the port rudder, so should provide decent readings while heeled. I should also have plenty of distance from prop cavitation, as well as being clear of errant feet using the boarding ladder. I probably could have eliminated the flat bar, but I really didn't want to drill holes below the waterline. Although it would have only been into the water ballast tank, and inward leakage wouldn't be a problem, I didn't want to have to worry about outward leakage from the tank.
Anyway, I am now mentally prepared to drill my first hole in my new boat! I suspect it won't be the last.
Thanks again for the suggestions.
Mark M.

[Frank C]

Sounds neat 'n all, but as to my X, I wouldn't run the cable thru the motor well's drainline. That drain is already too small. Take a close look when you stoop down and start installing.

[mark,97x]

on my it is stuck with plumbers putty next to the ballast tank behind the head in the bildge,,used to have it under the cooler spot but get less interference now(this new location was suggested by "sloop john b"),also was planning on replacing putty with epoxy but never saw the need as work good as is

[Dimitri-2000X-Tampa]

I agree with Frank. That drain tube is already on the small side and has to be "blown out" with high pressure water ever few months or it gets slow...and I don't park under any trees that could make the situation even worse. Running a wire through there would definitely make that thing clog up even worse...and it may not be too good for the wire either unless you have one that can stay immersed all the time.

For the record, my bronze transducer is mounted in the hull itself, in the rear port area between the ballast tank tubes. This was installed by the dealer before I bought the boat second hand. Never really bothered me much due to the fact that my previous sailboat probably had about 10 thru-hulls for various reasons. I suspect that with a proper installation, you would never have to worry about leakage...and mine always works perfectly, regardless of speed or sea conditions. Haven't taken it into very deep water so far though..probably about 80 feet max.